What this code means
U0146 may indicate a PF-CAN communication problem involving the PCM and the CAN gateway.
What the vehicle may do
- The vehicle may show network-related warning behavior.
- Some module information may not be shared normally.
- The code can set if the CAN gateway does not start normally.
Possible fault areas
- Possible CAN gateway startup concern.
- Possible CAN gateway power or ground circuit concern.
- Possible PF-CAN communication path concern.
- Possible abnormal information being sent from the CAN gateway.
Diagnostic path
Opening context
On this Civic, U0146 may point to a PF-CAN communication problem between the PCM and the CAN gateway. In plain terms, the PCM may not be getting the gateway message it expects, or the information coming from the gateway can be abnormal. Depending on the fault state, the vehicle may show network-related warning behavior, modules may not share information cleanly, or the code can set because the gateway did not start up normally. The broad areas to keep in mind are gateway startup, gateway power and ground, and the PF-CAN communication path itself.
Start with the basic checks
Before getting into the code-specific checks, start with the basic troubleshooting approach so the setup is clean and you are not skipping the foundation of the diagnosis. Then, before chasing the network side of this code, check the CAN gateway power and ground circuit first. That matters because this code may be stored from a power or ground failure at the gateway, and a gateway that is not powered or grounded correctly can look like a communication failure to the PCM.
Move into the communication path
If the gateway power and ground check does not explain the fault, the next diagnostic direction is the communication path for the bus connection to the gateway. Keep it disciplined: you are proving whether the PCM can receive the expected gateway communication over the PF-CAN line, or whether the information coming from the gateway is abnormal long enough for the fault to set.
Confirmation action
For the confirmation action, turn the vehicle to ON mode and wait 6 seconds. That gives the system the required startup window for this check, so the PCM can determine whether the gateway communication is normal or still abnormal.
Takeaway
The key with U0146 is to separate a gateway power or ground problem from an actual PF-CAN communication problem. Confirm the gateway can start normally, then continue the gateway communication checks without skipping ahead. For more diagnostic training, visit stepdiagnostics.com.
Final check
Diagnose U0146 by checking gateway power and ground first, then continue into the gateway communication path and confirm the condition with the specified ON-mode wait.
For more guided automotive diagnostics, visit STEP Diagnostics.
